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Math Help - quick question about ln x (working with derivatives

  1. #1
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    quick question about ln x (working with derivatives

    I am working with derivatives of the natural log.

    in the most recent example. it was to find the derivative of f(x) = x (ln x)^3

    f'(x) = (1)(ln x)^3 + x d/dx (ln x)^3

    d/dx (ln x)^3 is 3(ln x)^2*(1/x) which becomes [3 (ln x)^2]/x but then in the example it shows [3 (ln x)^2/x] just becomes 3 (ln x)^2. what happens to the x on the bottom?
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  2. #2
    Ted
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    Because of :

    Quote Originally Posted by colorado View Post
    f'(x) = (1)(ln x)^3 + x d/dx (ln x)^3
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  3. #3
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    ah sheesh, haha. thank you
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  4. #4
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    Hello, colorado!

    in the most recent example. it was to find the derivative of f(x) = x (ln x)^3

    f'(x) = (1)(ln x)^3 + x d/dx (ln x)^3

    d/dx (ln x)^3 is 3(ln x)^2*(1/x) which becomes [3 (ln x)^2]/x
    but then in the example it shows [3 (ln x)^2/x] just becomes 3 (ln x)^2.
    What happens to the x on the bottom?

    You forgot the x in front . . .

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